Conventional lug loaders or singulators (hereinafter collectively referred to as either lug loaders or singulators) have been found to be inadequate at higher feed speeds. They are also limited in their ability to both singulate and allocate lumber. When lumber is of varying widths and varying in thickness, or bowed, as may be predominant in curve sawing mills, cupped or crooked, it becomes increasingly difficult to handle the lumber at desirable higher speeds.
An example of a conventional lug loader is that taught in U.S. Pat. No. 3,923,142 which issued to Rysti on Dec. 2, 1975. In that patent the means for stopping work pieces prior to being singulated is only briefly mentioned. In particular, what is being taught is singulating boards by use of supporting arms rotating around a closed loop, the orientation of the supporting arms controlled by curved deflectors. Pressing arms in opposed radial pairs, are rotatably mounted above the supporting arms to synchronously clamp a board onto a supporting arm. Downstream flow of the mat of boards is arrested by a stop on each supporting arm. None of the advantages of the synchronized duckers of the present invention are taught or suggested. Rysti also does not disclose a mechanism for allocating or missing a lug space, especially at high speeds. The need to miss lug spaces arises for example where it is desirable to "cut-in-two" a long piece of lumber to meet mill requisites. In a "cut-in-two" situation there is a need to create an empty lug space behind the board. To achieve a "cut-in-two", a drop saw including a device to lift and set the cut length into the following lug space is provided up-stream on the lugged transfer.
At high speed, deliberately and accurately missing a lug space, which it is an object of the present invention to provide, requires a fast acting method to momentarily deactivate all feed and clamping devices, and subsequently to reactivate those apparatus in the brief time available as the closely spaced lugs are rotated past the singulator.
It is also an object of the present invention to provide for specific board allocating patterns required in the delivering of spacing sticks to a stick placer and its associated stacker to allow placing of sticks on lumber packages possibly having different package lengths.
Applicants are also aware of U.S. Pat. No. 5,518,106, which issued to Allard on May 21, 1996. Allard discloses using fixed pick-up shoes mounted onto rotating discs for engaging and supporting boards being singulated. Fixed shoes however, have the disadvantage that they may mark the underside of the board as the board is translated over the top of the disc and as the board is released. If a board is planned or finished, for example destined for cabinet making or the like, then any marks from the shoe or overhead clamp will reduce the value of the board. Allard also discloses a speed-up belt to pull the board away from the fixed shoes at the top of the disc to prevent the board from being flipped over as the board is released from the shoes. In some mills the boards have been marked for trimming and grading before the lug loader. Thus if the board has been flipped over by the singulator, as may occur in the case of the Allard device, the board must be flipped back by hand to read the mark. This can be difficult in a high speed application.
Many lug loaders in the prior art, particularly those operating at slower feed speeds, require that, in order to stop the delivery of boards to the singulator, the board mat moving downstream into the singulator device must be pushed back upstream by the stopping means, that is, forced away from the fixed pick-up shoe and clamping device. Worse yet, in some prior art devices the board delivery mechanism must be brought to a complete stop. Both pushing the mat of boards back upstream, and stopping the board delivery mechanism, can be impractical at high speed, a problem which is not adequately dealt with in the prior art.
It is therefore an object of the present invention to produce an apparatus wherein the delivery of boards is more controlled, with a simple means for stopping, activating and deactivating both a clamping means and a rotating pickup shoe simultaneously, allowing more precise and faster pick-up and delivery of spaced and allocated boards.
It is further an object of the present invention to produce an apparatus that has a quick acting stopping device for stopping the flow downstream of a board mat adjacent the singulator, wherein the stopping device has an adjustable dwell.
It is yet another object of the present invention to produce an apparatus that reduces the likelihood of leaving marks on the board by the pick-up and clamping device.
It is still another object of the present invention to produce an overhead clamping apparatus that can be retrofitted to existing lug loaders of the general type to improve the speed and consistency of delivery of boards by said existing lug loaders.